upto0013 writes: A new study shows that a common sleep disorder may be a sign of dementia or Parkinson's disease up to 50 years before the disorders are diagnosed.

The new research was published in Neurology, the medical journal of the American Academy of Neurology. The study, based on Mayo Clinic records, suggested that people who experience rapid eye movement sleep behavior disorder could one day come down with the degenerative aging disease.

Sufferers of REM sleep behavior disorder, dubbed "Jimmy legs" in the sitcom "Seinfeld," often act out their dreams with violent movements, such as punching or kicking.